There are basically two types of techniques for winding a web into a roll. These are a surface-winding technique, in which a driving force is applied to an outer surface of a rolled web, and a center-winding technique, in which a core is rotated to wind a web into a roll on the core. In many instances, the center-winding technique is preferred over the surface-winding technique. For example, the surface-winding technique encounters problems in properly driving the rolled web when the web has a printed, textured or slippery surface.
In the past, center-winding apparatus have been disclosed which are capable of continuously winding a web into a plurality of rolls (see, for instance, Young U.S. Pat. No. 3,472,462 and Hellemans U.S. Pat. No. 3,501,104). Such continuous center-winding apparatus have employed a single knife to sever the web between winding operations. The use of a single knife is disadvantageous because the web must be tensioned so that the knife can cut it. Some materials have an insufficient tensile strength to withstand the tension required to cut them using a single knife. Other materials are too heavy to tension to the extent necessary to perform a successful cutting operation using a single knife.
Breacker et al. U.S. Pat. No. 3,443,769 and Smolderen U.S. Pat. No. 3,871,595 disclose center-winding apparatus in which a pair of knives are employed to cut a web. However, both of the apparatus require the repositioning of a rolled web at or near the termination of a winding operation. Also, both of the knives of each apparatus must be pivoted into cutting positions at the termination of a winding operation. Such repositioning of the rolled web and pivoting of the knives are time consuming. Thus, an operator performing an unscheduled cutting operation, for safety reasons or otherwise, might not be able to accomplish such an operation as quickly and efficiently as desired.